The present invention relates to a longwall mining machine of the type having a pivot arm which supports a cutter drum for rotation about an axis for working a mine face. In a mining machine of this type, the rotating cutter drum cuts the material being mined and is provided with spiral flights which assist in loading the mined material onto a face conveyor. The cutter drum often carries nozzles on the periphery of its spiral conveying flights for directing trickle of liquid onto the face area being mined. The flow of liquid to the nozzle is controlled by valves spaced around the axis of the drum, these valves being actuated such that liquid is delivered only from those nozzles immediately adjacent the working face.
ln U.S. Pat. No. 1,473,498, a cutter drum assembly for mining machines is disclosed wherein the nozzles on the periphery of the cutting drum are connected through conduits and valves to a source of liquid under pressure, the valves being actuated to deliver liquid to the nozzles immediately adjacent the working face by a cam which does not rotate with the cutter drum itself.
Another cutter drum assembly for mining machines is disclosed in U.S. Pat. No. 4,212,497 wherein a valve system is provided for nozzles on the periphery of the cutter drum, the valve taking the form of a recess which communicates with a high pressure passageway extending through the shearer drum shaft and which extends over the shearer drum periphery through an angle corresponding to the activation zone of the nozzles. The recess is disposed in a component which does not cooperate with the shearer drum (e.g., the drum-carrying shaft which does not rotate with the drum) or a non-rotating tube mounted centrally inside the shearer drum drive shaft. The recess in the aforesaid arrangement is covered by means of the cutter drum hub which extends around the drum shaft and is provided with appropriate seals, or by the drum drive shaft which extends in a liquid-tight manner around the tube, both the latter shafts co-rotating with the shearer drum. Radial conduits communicating with the various nozzles or nozzle groups extend into that bore portion of the cutter drum hub or drive shaft which covers the recesses.
In a shearer drum such as that described in U.S. Pat. No. 1,473,498, the various valves are actuated through the agency of a cam, a system which requires delicate linkages to transmit the actuating movement. On the other hand, in a construction such as that shown in U.S. Pat. No. 4,212,497, the operative period of the high-pressure liquid delivered from the nozzles is controlled directly by the cutter drum drive shaft and the stationary tube inside the shaft bore, or by the cutter drum shaft and the cutter drum hub therearound. Because of the high pressure of the liquid forced through the nozzles, the control faces of the drum parts which slide one on the other have to be manufactured to extremely close tolerances if a liquid-tight seal is to be achieved. This extreme precision makes production expensive. Also, a mechanism of this kind experiences heavy wear and impairs rotation of the drum to some extent.